Quantum recently discussed electric vehicles in Australia and their late arrival.
One of the speakers mentioned that the batteries in the e vehicles could be used with the home solar systems for battery storage.
Could choice or the choice community offer insight into this idea.
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Welcome @Caveman. This may provide some information on this subject.
https://www.racv.com.au/royalauto/transport/electric-vehicles/bidirectional-charging-explained.html
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Welcome to the Community @Caveman
There is some discussion of V2G (vehicle to grid) in this site.
If you search V2G you should see some results.
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Further to the linked article, such systems are often referred to as V2H or V2G. Vehicle to Home and Vehicle to Grid.
An Australian trial of V2G technology in the ACT utilising 51 vehicles was announced in July 2020. I’ve not noted any recent updates. As background:
Our vision is that a small capacity home battery backed up with a BEV and V2H connection may be the quickest and only real solution for Australians to directly lower their personal carbon footprints. Energy independence and cost benefits may also be achievable.
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That’s a bit of an unknown at this point, given the low FiTs available, and the depreciation of battery capacity when cycled for home use as well as for vehicular use.
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Agreed, and worth pointing out.
The future for the Grid connected supply is also ‘a bit of an unknown at this point’, given the indecision on setting comprehensive climate GHG reduction targets.
As an aside - the shift to TOU and demand pricing of supply; the likely ability to export using variable FiTs (demand/time of day); and rate of development of DER are all factors that will impact future electricity costs.
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Some of these car batteries after they become unfit for the vehicle may have a useful life after that as pure household storage for some further years. One way to recycle without complete disassembly perhaps?
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I have read articles on that suggestion.
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People have been extracting the battery from wrecked electric cars for years and using them for off-grid batteries. I doubt that you could connect them to the grid legally at the moment though.
Lots of work involved in dismantling and reconfiguring to a suitable voltage for those keen to try it for off-grid.
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We are drifting a little.
Would that depend on the inverter selected?
Assuming the system has a qualified designer, an authorised person installs the inverter and the battery location complies, what gets connected on the DC side if it is ELV may not be a concern. It would need some further enquiry to be sure.
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Drifting off to sleep? 
rules about re-using EV batteries is on topic IMHO
The inverter has to comply with the standards, as does the battery, so once a particular EV-battery-inverter system is passed as compliant, it will be ok. Gaining compliance and approval to grid connect a cobbled together battery removed from a crashed car might be rather difficult!
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That’s understood. Apologies for offering only a part response on the battery requirements.
Category 3 per AS5139?
Renew offered a view at the time the standard was released. And the CEC issued the following advice to installers.
The rest is up to the approved designer.
Note:
The first reply to the OP assumed the enquiry related to V2G.
As you point out for the alternate interpretation, recycling EV batteries into home battery systems is more challenging. The CEC included Category 3 batteries in it’s advice to installers. Rightly or wrongly I’ve assumed that a recycled EV battery is acceptable. It’s up to the approved designer to decide what additional components are required to match the battery and inverter/charge controller to meet the standard, and protect the battery. It’s certainly more effort compared to choosing a Category 1 or 2 approved battery.
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Cells in EV batteries degrade; a time is reached (in x years, well over 8 years) that the EV battery is no longer fit for powering the vehicle. At that point in time one of the following can happen - the battery is repurposed as a household battery, the battery has the dead cells identified and replaced (and continues as a battery in an EV), or the materials in the battery are recycled (Tesla published 100% recycling capability in 2021).
An “old” EV battery repurposed as a household battery would be very effective.
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ARENA article about repurposing EV battery to power your home:-
“when a battery has depleted to the point where it cannot continue powering your electric car it can still have as much as 80 per cent of its original charge.”
" Relectrify has developed a “plug and play” system that brings new life to old lithium-ion batteries, allowing them to be repurposed, storing energy for households with solar panels."
"“We estimate these batteries, when they are no longer useful in the cars, still have about 2000 cycles left,” Dr Muenzel said.
“So if you reuse these in a solar home, charge and discharge them once a day … you would still get about six or seven years out of them.
“In motor homes, which you usually only use a number of months a year, the batteries will last far longer yet.”
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Do we know what became of this project?
The ARENA article is dated from 2017.
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I priced batteries from Relectrify a couple of years ago, and they were very expensive for a used battery. They were going to send me more info when they became available to buy, but I don’t think heard from them again.
Motorhome life of the battery would not be as long as you might expect, batteries not only have a cycle life, but also a calendar life. The capacity decreases over time, whether or not they are in use.
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